Pressure responsive resistor



June 6, 1961 v. R. PALMER] 2,987,687

PRESSURE RESPONSIVE RESISTOR Filed April 28, 1960 INVENTOR. VICTOR R.PALMER! ATTOR N EY United States Patent 0,

2,987,687 PRESSURE RESPONSIVE RESISTOR Victor R. Palmeri, Weehawken,N.J., assignor to Space Dynamics Corporation, Clifton, N.J., acorporation of New Jersey Filed Apr. 28, 1960, Ser. No. 25,462

12 Claims. (Cl. 338-36) This invention relates to pressure responsiveresistors, and more particularly, concerns devices sensitive to changesof applied pressure and adapted to vary its electrical resistance inaccordance with such changes in pressure.

In electrical or electronic circuitry it is frequently desirable toinclude as a component thereof resistor means whose resistance valueschange in accordance with pressures applicable to the component. Thuswith instrumentation controls regulation thereof may be responsive topressure conditions as well as other environmental factors orcharacteristics.

Accordingly, an object of this invention is to provide an improvedpressure responsive resistor which is compact and of minimum bulk, whichmay be readily accommodated to small or irregular spaces, and whichshows high sensitivity to small changes in pressure.

Another object of this invention is to provide in a device of thecharacter described, a body of material of predetermined compositionwhich is operative to sense small variations in pressure applied to thebody and to change its resistance accordingly.

A further object of this invention is to provide in a device of thecharacter described, a pressure responsive element in the form of alayer of material whose composition may be adjusted in accordance withthe magnitudes of the pressure ranges to be sensed.

Still another object of this invention is to provide a pressureresponsive resistor in flat, flexible form which is readily adapted toconform to supporting surfaces of varying shape, yet is highly sensitiveto variations in pressure so as to change its resistance values.

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

In the drawing, FIG. 1 is an enlarged transverse sectional view of adevice embodying the invention;

FIG. 2 is a top plan view thereof.

Essentially, the device of the instant invention comprises a body ofmaterial of predetermined composition; the body being suitably enclosedand provided with electrodes or terminals in contact with oppositesurface portions of the body. The assembly may be in thin flat form andmay be flexible so as to readily confirm to an irregular supportingsurface. The body of material is made up as a particulate mixture ofsilicon and rare earth compounds, such as the oxides; the oxide beingpresent in relatively small amounts.

The body of material may have its composition adjusted by the additionof small amounts of powdered metal and inert fillers, to suit particularpressure ranges; and may also contain small amounts of a flexiblebinder.

Thus, as shown in FIGS. 1, 2; a pressure responsive resistor embodyingthe invention, is generally shown at 10. The same is in flat strip formcomprising a pair of opposed strips 11, 12 of synthetic resin such asTeflon (polytetrafluoroethylene), polystyrene, vinyl, copolymer or thelike. The strips 11, 12 enclose and seal a body 13 of predeterminedcomposition; electrodes or terminals 14, 15 being disposed in contactwith body 13 on opposite sides thereof.

The body 13 is made up in the form of a mixture of silicon and a smallamount of a rare earth compound such as the oxide of gadolinium,neodymium, samarium, scandium or yttrium. The silicon may be present inamounts 2,987,687 Patented June 6, 1961 ranging from about to about 99%;the rare earth oxide instances, the mixture may include small amounts ofpowdered tungsten, nickel or chromium, ranging up to about 3 Thus, in aresistor 10 for sensing variations of pressure within a relatively highpressure range, body 13 may be made up of 92% silicon, 4% gadoliniumoxide and 4% zirconium dioxide. The several materials are thoroughlyadmixed in particulate form and then suitably agglomerated in thin sheetor block form for assembly with strips 11, 12.

Strips 11, 12 are previously treated on one surface thereof to formelectrodes 14, 15 thereon, as by cathode sputtering of electrodepositionof a suitable metal film to constitute said electrodes; which may be ofsilver, gold, platinum or the like. Wire leads 16, 17 may extend fromelectrodw 14, '15, to provide electrical connecting means.

The strips 11, 12 with body 13 therebetween, are sealed together by asuitable elastic sealant 18 extending about the periphery of said stripsand adhering their opposed marginal edge portions. Sealant 18 may be ofa rubbery or plastic character and preferably of a chemical resistantnature.

Another formulation for body 13 comprises 96% silicon, 1% yttrium oxideand 3% silicon dioxide. The formulation was prepared in agglomeratedform and assembled with enclosing strips 11, 12, as previouslydescribed. Such device is particularly effective for intermediatepressure ranges.

For relatively low pressure ranges, body 13 may be made up of 98%silicon, 0.5% gadolinium oxide, 0.3% zirconium dioxide, 0.2% rubberbinder and 1% tungsten powder.

The material making up body 13 is in powdered form with a particle sizeranging from about .0001 to about .025 Upon adding small amounts ofplastic elastic binder, the resultant flexible body together with itsflexible enclosure may be readily mounted on curved or irregularsurfaces.

As various changes might be made in the embodiments of the inventionherein disclosed without departing from the spirit thereof, it isunderstood that all matter herein shown or described shall be deemedillustrative and not limiting except as set forth in the appendedclaims.

Having thus disclosed my invention, I claim as new and desire to protectby Letters Patent:

1. A pressure responsive resistor comprising a flexible body of materialand a pair of electrodes respectively in contact with opposite portionsof said body, said body comprising a major portion of silicon and aminor portion of a rare earth material selected from the groupconsisting of gadolinium, neodymium, Samarium, scandium and yttriumoxides.

2. A pressure responsive resistor comprising a body of material and apair of electrodes respectively in contact with opposite portions ofsaid body, said body comprising a major portion of silicon and a minorportion of a compound selected from the group consisting of gadolinium,neodymium, Samarium, scandium and yttrium oxides.

3. A resistor as in claim 2 wherein said body further includes a minoramount of powdered metal.

4. A resistor as in claim 2 wherein said body further includes a minoramount of elastic binder.

5. A resistor as in claim 2 wherein the silicon is present in amounts offrom about 90 to about 99% and the oxide is present in amounts of fromabout 1 to about 10%, all by weight.

6. A resistor as in claim 2 wherein said body comprises 3 agglomeratedparticles, said particles from about .0001 to about .025.

7. A pressure responsive resistor comprising a body of material, asealed enclosure for said body of material, said enclosure comprisingelectrical insulating sheet material, metal film electrode means on theinner surface portions of said enclosure and in contact with opposedsurface portions of said body of material, said body of materialcomprising a major portion of silicon and a minor portion of a rareearth material selected from the group consisting of gadolinium,neodymium, sarnarium, scandium and yttrium oxides.

8. A resistor as in claim 7 wherein said body of material furtherincludes a minor portion of elastic binder,

having a size of 2,987,687 i A V 9. A resistor as in claim 7 whereinsaid enclosure comprises synthetic resin sheeting.

10. A resistor as in claim 8 wherein said sheeting is formed ofpolytetrafluoroethylene.

11. A resistor as in claim 7 wherein said rare earth oxide is gadoliniumoxide.

12. A resistor as in claim 7 wherein said silicon is present in amountsof from about 90 (to about 99% by weight.

References Cited in the file of this patent UNITED STATES PATENTS1,039,463 Thomson Sept. 24, 1912

1. A PRESSURE RESPONSIVE RESISTOR COMPRISING A FLEXIBLE BODY OF MATERIALAND A PAIR OF ELECTRODES RESPECTIVELY IN CONTACT WITH OPPOSITE PORTIONSOF SAID BODY, SAID BODY COMPRISING A MAJOR PORTION OF SILICON AND AMINOR PORTION OF A RARE EARTH MATERIAL SELECTED FROM THE GROUPCONSISTING OF GADOLINIUM, NEODYMIUM SAMARIUM, SCANDIUM AND YTTRIUMOXIDES.